This application claims benefit of Korean Patent Application No. P2000-50429, filed on Aug. 29, 2000, the entirety of which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display and a method for fabricating the same, which has large aperture and can improve a poor picture quality caused by vertical cross talk.
2. Background of the Related Art
A related art liquid crystal display is provided with a liquid crystal panel, a light source, and a driving circuit. The liquid crystal panel has first and second substrates, and liquid crystal injected between the two substrates. The second substrate has a black matrix, a color filter layer, and a common electrode.
The first substrate has a plurality of gate lines running in one direction at fixed intervals, a plurality of data lines running in one direction perpendicular to the gate lines at fixed intervals, and an LCD array at crossing parts of the gate lines and the data lines.
In an LCD array region, a space region between the gate lines and data lines is a pixel region, in which a pixel electrode and a thin film transistor are provided. That is, the thin film transistor is provided with a gate electrode connected to the gate line, a source electrode connected to the data line, a data electrode connected to the pixel electrode, for being turned on selectively in response to a signal to the gate line to transfer a data signal from the data line to the pixel electrode. The gate lines and the data lines are electrically connected to driving circuits.
Vertical cross-talk in the liquid crystal display, caused by parasitic capacitance Cds between the source electrode and the drain electrode, degrades a picture quality as a source voltage (a data signal) to be provided to the pixels on a vertical (data) line influences the liquid crystal pixel voltage. The cross-talk mostly occurs as a static capacitance between the data line and the pixel electrode is increased. Research has been performed with a goal to reduce the vertical cross-talk in a liquid crystal display with a large aperture. In order to achieve the large aperture, an organic insulating film is used as a passivation film deposited between the data line and the pixel electrode, and the pixel electrode is overlapped with and edge of the data line.
A related art liquid crystal display and method for fabricating the same will be explained, with reference to the attached drawings. FIG. 1 illustrates a layout of a first substrate of the related art liquid crystal display, and FIG. 2 illustrates a section of the related art liquid crystal display across line I-Ixe2x80x2 in FIG. 1, showing a pixel electrode, a data line, and a drain electrode.
Referring to FIGS. 1 and 2, the related art liquid crystal display is provided with an active layer 102, a channel layer of a thin film transistor in an active region defined on an insulating substrate 101, a gate insulating film (not shown) on the active layer 102 to surround the active layer 102, and a gate electrode 103a crossing a central part of the active layer 102 on the gate insulating film. The gate electrode 103a is a projection from the gate line 103 running in one direction. There are source/drain regions in the active layer on both sides of the gate electrode 103a, an interlayer insulating film 104 on an entire surface inclusive of the gate electrode 103a, and first contact holes 106 to expose the source/drain regions in the active layer 102 by etching the interlayer insulating film 104 and the gate insulating film. The source electrode 105a, the drain electrode 105b, and the data line 105 are formed at each of the contact holes 106 and on the interlayer insulating film 104. The data line 105 and the gate line 103 cross each other. An organic insulating film 107 is formed on the interlayer insulating film 104 inclusive of the source electrode 105a, the drain electrode 105b, and the dateline 105. The organic insulating film 107 has a flat surface. There is a second contact hole 108 in the organic insulating film 107 to expose the drain electrode 105b, and a pixel electrode 109 of ITO (Indium Thin Oxide) in the second contact hole 108 and on the organic insulating film 107. The pixel electrode 109 overlaps upper parts of edges of the data line 105, except the central part thereof.
Referring to FIG. 2, in a large aperture structure, a distance xe2x80x98bxe2x80x99 between the pixel electrode 109 and the data line 105 is the most important element in view of the vertical crosstalk. That is, the greater the distance xe2x80x98bxe2x80x99, the smaller the parasitic capacitance between the pixel electrode 109 and the data line 105, that improves the poor picture quality caused by the vertical crosstalk. However, the distance xe2x80x98bxe2x80x99 can not be made greater because an increased distance xe2x80x98bxe2x80x99 necessitates an increase of an etch depth xe2x80x98cxe2x80x99 of the second contact hole 108 provided for bringing the pixel electrode 109 into contact with the drain electrode 105. In conclusion, xe2x80x98cxe2x80x99 is fixed depending on a dry etching (anisotropic etching) capability, xe2x80x98axe2x80x99 is fixed depending on xe2x80x98cxe2x80x99, and xe2x80x98bxe2x80x99 is fixed depending on xe2x80x98cxe2x80x99. For an example, when xe2x80x98cxe2x80x99=9500 xc3x85, xe2x80x98dxe2x80x99=3500 xc3x85, xe2x80x98axe2x80x99=1.3 xcexcm, and xe2x80x98bxe2x80x99=0.95 xcexcm. If xe2x80x98bxe2x80x99 is to be made thicker, then xe2x80x98cxe2x80x99 also has to be made thicker.
A method for fabricating the foregoing related art liquid crystal display will be explained. FIGS. 3Axcx9c3C illustrate sections showing the steps of a method for fabricating the related art liquid crystal display.
Referring to FIG. 3A, an active layer 102 (see FIG. 1) is formed on an active region defined on an insulating substrate 101, a gate insulating film (not shown) is formed on the active layer 102 to surround the active layer 102, and a gate line 103 (see FIG. 1) is formed on the gate insulating film to run in one direction, together with a gate electrode 103a (see FIG. 1) projected from the gate line 103 to cross a central part of the active layer 102. Source/drain regions are formed in the active layer on both sides of the gate electrode 103a. 
Then, as shown in FIG. 3B, an interlayer insulating film 104 is deposited on an entire surface inclusive of the gate electrode 103a, and the interlayer insulating film 104 and the gate insulating film are etched to expose the source/drain regions in the active layer 102, to form a first contact hole 106 (see FIG. 1). A metal layer is formed in respective first contact holes 106 to the source and drain regions and on the interlayer insulating film 104, and subjected to anisotropic etching, to form a source electrode 105a (see FIG. 1) in contact with the source region, a drain electrode 105b in contact with the drain region, and a data line 105 extended from the source electrode to be in a perpendicular direction to the gate line 103.
As shown in FIG. 3C, an organic insulating film 107 is coated on an entire surface of the source electrode 105a, the data line 105, and the drain electrode 105b, and a second contact hole 108 is formed on the organic insulating film 107 to expose the drain electrode 105b. An ITO (Indium Tin Oxide) is deposited on an entire surface of the organic insulating film 107 inclusive of the second contact hole 108, and subjected to anisotropic etching to expose a central part of the data line 105, and overlaps upper part edges of the data line 105, to form a pixel electrode 109.
However, the foregoing related art liquid crystal display, and a method for fabricating the same, have the following problem.
The thicker organic insulating film formed between the data line and the pixel for reduction of a parasitic capacitance between the data line and the pixel electrode requires a longer time period in etching a second contact hole to bring the drain electrode and the pixel electrode into contact. Accordingly, the related art has a limitation in providing a liquid crystal display, which reduces a vertical crosstalk while a large aperture is achieved, for improving a picture quality.
Accordingly, the present invention is directed to a liquid crystal display and a method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a liquid crystal display and a method for fabricating the same, which can reduce a vertical crosstalk while a large aperture is achieved, for improving a picture quality.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the liquid crystal display includes a first substrate having an active layer with source/drain regions formed therein, a gate line and a data line formed thereon extending in directions perpendicular to each other, a dummy gate insulating film and a dummy gate electrode both formed on the first substrate in fixed patterns isolated from the gate line, an interlayer insulating film on the first substrate inclusive of the dummy gate electrode with a step, a drain electrode formed on the interlayer insulating film to overlap on upper regions of the dummy gate electrode so as to be in contact with the drain region and have a step to the data line, the data line formed on the interlayer insulating film having a step to the drain electrode, a passivation film formed on the interlayer insulating film inclusive of the dummy gate electrode and the data line, a contact hole formed to expose the drain electrode overlapping the dummy gate electrode, and a pixel electrode overlapping upper edges of the data line and in contact with the drain electrode through the contact hole, thereby reducing a vertical crosstalk while a large aperture is achieved, to improve a picture quality.
In the other aspect of the present invention, there is provided a method for fabricating a liquid crystal display including a first substrate having an active layer with source/drain regions formed therein, and a gate line and a data line perpendicular to each other formed thereon, the method comprising the steps of (a) forming the gate line at the same time as forming a dummy gate insulating film and a dummy gate electrode both on the first substrate in fixed patterns isolated from the gate line, (b) forming an interlayer insulating film on the first substrate inclusive of the dummy gate electrode and the gate line so as to have a step, (c) forming the data line at the same time as forming a drain electrode on the interlayer insulating film to overlap on upper regions of the dummy gate electrode so as to be in contact with the drain region and have a step to the data line, (d) forming a passivation film on the interlayer insulating film inclusive of the dummy gate electrode and the data line, (e) forming a contact hole to expose the drain electrode overlapped with the dummy gate electrode, and (f) forming a pixel electrode on the passivation film to overlap upper edges of the data line and to be in contact with the drain electrode through the contact hole.
The present invention reduces a capacitance between the pixel electrode and the data line for reducing a vertical crosstalk, by forming an organic insulating film between the pixel electrode and the data line while a contact hole forming time period for providing a contact between the pixel electrode and the drain electrode is not increased because the thickness of the insulating film where the contact hole is formed is not increased.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.